Endoscopic device for locomotion through the gastro-intestinal tract

ABSTRACT

An endoscopic device for locomotion in a body cavity according to a prefixed advancing direction (A) comprising at least a variable length intermediate section ( 1   a,    21   a ) extending between a front end section ( 1   b,    21   b ) and a rear end section ( 1   c,    21   c ). First and second clamping means ( 7, 12, 27, 32 ) are integral to the front and rear section, for alternately grasping respective surrounding portions of wall (P) of the body cavity. Sucking means ( 13, 14, 37, 38 ) are associated to the first and second clamping means for creating a depression sufficient to cause the body cavity wall portions to collapse within the first and second clamping means while they are in an open condition. Means for actuating alternate extensions and retractions of the intermediate section and actuating means ( 6, 11, 26, 31 ) of the first and second clamping means are further provides for synchronous operation to generate a forward motion of the rear end section due to a retraction of the intermediate section, the wall portion (P) surrounding the first clamping means being firmly held therebetween, and to generate a forward motion of the front end section due to an extension of the intermediate section, the wall portion (P) surrounding the second clamping means being firmly held therebetween.

FIELD OF THE INVENTION

The present invention relates to an endoscopic device for locomotionthrough a tubular body cavity, in particular, but not exclusively,through the gastrointestinal tract, able to migrate in a prefixeddirection with so-called inchworm motion.

BACKGROUND OF THE INVENTION

Endoscopic devices for surgical or diagnostic procedure are alreadyknown. These devices are operated by the surgeon who directly imparts tothe device the forward motion through the patient's body. Surgicaland/or diagnostic instruments which are necessary to carry out eachspecific procedure, such as microarms, microcameras, and/or laseremitters are generally associated to these devices.

In order to make easier the surgeon's task there have been proposedendoscopic devices of the above mentioned type capable of asemi-autonomous movement within the body cavity of a patient, adaptingtheir shape, as far as possible, to the shape of the surrounding cavity.In this case, the walls of the body cavity act as a support forpropelling the device forward. For example, in U.S. Pat. No. 5,398,670there is disclosed an endoscopic instrument substantially formed by abellows-shaped tubular body, capable of extension and retraction, and bytwo end portions including respective inflatable balloon members, bymeans of which the front end portion and the rear end portionalternately engage by compression with the walls of the body cavitythrough which the device must be pushed forward. There is provision fora control system which operates the inflation and deflation of the twoballoon members and the extension and retraction of the tubular bodyaccording to a sequence such as to produce the advancement of the devicein the prefixed direction.

An endoscopic device of the same type is disclosed in U.S. Pat. No.5,906,591, in which, however, a vacuum pressure sufficient to produce,under the induced sucking conditions, a substantial anchorage of thefront and rear end portions to the cavity wall is created sequentiallyaround these end portions.

When the endoscopic device of the type described in the above citedpatents is destined to the locomotion through the gastro-intestinaltract, its anchorage to the cavity walls is not satisfactory, becausethis type of cavity is soft, slippery and often wet. Using balloon-typeendoscopic devices such that according to U.S. Pat. No. 5,298,670, evenif the intestinal wall is overextended, it is impossible to producesufficient traction forces due to extremely low friction coefficient ofthe gastrointestinal tract. Furtheremore, excessive overextension of theballoon will result in causing severe pain for the patient. A similarresult is obtained by increasing the suction in the case of theendoscopic device of U.S. Pat. No. 5,906,591, with the drawback that,when the degree of vacuum is increased over a certain extent,undesirable lesions may appear.

In order to improve the anchorage of the endoscopic devices of the abovementioned type it has proposed to equip them with auxiliary anchoringmeans of various shapes, which, however, increase the structuralcomplexity and the length of the device and increase the patientdiscomfort and the risk of damage of the involved tissues.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an endoscopic deviceof the semi-autonomous locomotion type through a body cavity such as thegastro-intestinal tract, capable of assuring a suitable anchorage to thebody cavity thereby allowing its advancement through it, without givingrise to any of the problems encountered with the similar known devices.

Another object of the present invention is to provide an endoscopicdevice of the above mentioned type for achieving a suitable anchorage tothe cavity wall by means of structurally simple solutions allowing thesize of the device to be kept small.

These object are reached with the endoscopic device for locomotion in abody cavity in a prefixed advancement direction according to the presentinvention, comprising at least a variable length intermediate sectionextending between a front end section and a rear end section withrespect to said direction and first and second clamping means integralto the front end section and, respectively, the rear end section, forselectively grasping respective surrounding portions of the wall of thebody cavity. Associated to the first and second clamping means suctionmeans are provided for creating a vacuum sufficient to cause thesurrounding portions of the body cavity walls to collapse within thefirst and the second clamping means, when they are in their opencondition, to allow a firm grasping when said clamping means are closed.Means For operating alternate elongations and retractions of theintermediate section and means for operating the first and secondclamping means, synchronously operated to cause an advancement of therear end section device in the prefixed direction following a retractionof the intermediate section when the respective portion of surroundingwall is firmly engaged with the first clamping means, and to cause anadvancement of the front end section in the same direction following anelongation of the intermediate section when the respective surroundingwall portion is firmly engaged within the second clamping means.

Furthermore, the present invention provides a method for producing thelocomotion through body cavities of an endoscopic device, by means ofsuccessive extensions and retractions of at least one variable lengthintermediate section thereof according a prefixed direction definingfront end section and a rear end section of the device, to which firstand second clamping means are respectively associated selectivelyoperable from the outside synchronously with the successive extensionsand retractions of the intermediate section. The method is characterizedby inducing selectively by suction a pneumatic depression incorrespondence to one of the first or the second clamping means in theiropen condition, the depression being such that to cause the surroundingportion of body cavity wall to collapse within said clamping means, andclosing said clamping means to grasp said surrounding wall portion andfirmly anchoring to it the respective end section to allow the freemovement of the other end section in the prefixed direction.

The main advantage of the endoscopic device of the invention consists inthat it can migrate through a tubular body cavity in every conditionwhatever the available friction forces and the compliance of the bodycavity are

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the endoscopic deviceaccording to the invention will become more apparent from the followingdescription of exemplifying, not limiting embodiments thereof, made withreference to the annexed drawings, in which:

FIG. 1 is a longitudinal sectional view of a first embodiment of theendoscopic device according to the present invention;

FIGS. 2 a-2 k show and advancement cycle of the device of FIG. 1;

FIG. 3 is a longitudinal sectional view of a second embodiment of thedevice according to the present invention;

FIG. 4 is a cross sectional view of the endoscopic device of FIG. 3taken along arrows IV—IV;

FIG. 5 is a longitudinal sectional view of the endoscopic device of FIG.3 taken along arrows V—V of FIG. 4;

FIGS. 6 a, 6 b, 6 c schematically show the operation of the clampingmeans integral to the rear end of the endoscopic device of FIG. 3;

FIGS. 7 a, 7 b schematically show the operation of the clamping meansintegral to the front end of the endoscopic device of FIG. 3;

FIGS. 8 a-8 g show and advancement cycle of the endoscopic deviceaccording to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, it has been generally indicated at 1 anendoscopic device according to the present invention. It comprises anintermediate section 1 a of a tubular shape, extending between two endsections called front end section 1 b and rear end section 1 c, theterms “front” and “rear” being referred to a reference directionindicated at A. Clearly, the endoscopic device will be able to move inthe body cavity in a forward and a backward direction. The tubularintermediate section 1 a is formed by a wall 2 made of elastic andflexible material shaped like a bellows and delimiting a cavity 3 forcontaining a fluid, for example air. The intermediate section ends witha front flange 2 a and a rear flange 2 b through which it is connectedto front end section 1 b and rear end section 1 c respectively.

Front end section 1 b of the device is formed by a stem 4 fixed to frontflange 2 a at a flanged end 4 a thereof and to a front head 5 of thedevice at the other end. Fixed to flanged end 4 a of stem 4, at theopposite side of flange 2 a, is a bellows member 6 which is integral toa jaw 7 a of a first clamp 7 (also called front clamp) slidably mountedon stem 4 and fixed to the free end of bellows 6. The other jaw 7 b offirst clamp 7 is constituted by a face of front head 5 perpendicular tothe axis of stem 4 and faced toward first jaw 7 a.

Rear end section 1 c is formed by a rear head 8, from which a tubularconnector 9 extends, connected to a flanged end 10 a of a stem 10. Fixedto flanged end 10 a, at the opposite side of rear head 8, is a bellowsmember 11 integral to a jaw 12 a of a second clamp 12 (also called rearclamp) coaxially and slidably mounted on stem 10, the other jaw 12 b ofsecond clamp 12 being formed by a plate fixed to the end of stem 10 atone side thereof and to rear flange 2 b of intermediate section 1 a atthe other side.

Tubular connector 9 puts into communication the device with an externalcontrol system, of the conventional type, for example as described andshown in FIG. 3 of U.S. Pat. No. 5,906,591, comprising a source (50) forselectively providing a positive or negative pressure to the variousparts of the devices as will be explained below. More precisely,connector 9 houses pneumatic conduits extending in a substantially axialway within device 1 (as schematically shown in FIG. 1), each of thembeing able to both feed compressed air to and suck air from chamber 3 ofbellows-shaped intermediate section 1 a (conduit 40), bellows member 6and 11 controlling the operation of clamps 7 and 12 (conduits 41, 42),as well as to/from a surface portion of stems 4 and 10 comprised betweenjaws 7 a, 7 b and 12 a, 12 b, respectively, of clamps 7 and 12, throughdiametral ducts 13 and 14 extending from respective axial ducts 15 and16 formed in stems 4 and 10, communicating with respective pneumaticconduits housed within connector 9. A further pneumatic conduit. 43outflows from front head 5 to blow air jets useful to assisting forwardmotion of the device. In particular, pneumatic conduits passing throughintermediate section 1 a are helically arranged within chamber 3 asschematically indicated at 44 in FIG. 1.

The operating cycle of the endoscopic device is now described withreference also to FIGS. 2 a-2 k (the parts being in turn under pressureare shown as hatched). By creating suction conditions at rear clamp 12 asubstantially annular portion P of the surrounding wall of the bodycavity is caused to collapse between jaws 12 a, b which, by adduction ofcompressed air within bellows 11, close against each other firmlygrasping wall portion P (FIG. 2 a). Through radial duct 13 of stem 4 airis blown against cavity wall P to cause its displacement from front endsection 1 b of the device (FIG. 2 b). Then compressed air is fed tobellows 2 which elongates pushing front end section 1 b of the deviceforward (FIG. 2 c). At this point, a depression is created between jaws7 a, b of front clamp 7 which causes a substantially annular portion ofthe surrounding cavity wall P to collapse therebetween. By adductingcompressed air bellows 6 is caused to elongate and clamp 7 closes firmlygrasping cavity wall (FIG. 2 e). Bellows 11 is then retracted bydepression to open clamp 12 (FIG. 2 f) releasing the grasped cavity wallwhich is displaced back from rear end section 1 c of the device by meansof air jets through radial duct 14 of stem 10 (FIG. 2 g). Rear endsection 1 c is then pulled forward by bellows 2 which retracts due todepression induced therein (FIG. 2 h). At this point, rear clamp 12grasp a new annular portion of surrounding cavity wall P by creation ofa depression between jaws 12 a, 12 b (FIG. 2 i) and closure of rearclamp 12 (FIG. 2 j), while front clamp 7 opens to release the graspedannular wall portion. Then the cycle is repeated with a new advancementstep.

In order to improve the grip of jaws 7 a, 7 b and 12 a, 12 b of frontclamp 7 and rear clamp 12 respectively, a circular groove 17 is formedon one of their opposed faces and a corresponding step 18 for engagingwith groove 17 is formed on the other face. Advantageously all the edgesof the grip surfaces are beveled to avoid any tissue damage.

A second embodiment of the endoscopic device according to the inventionis shown in FIGS. 3, 4, 5, 6 a -c and 7 a, b. In the figures, 21 aindicates an intermediate tubular section of the device formed by abellows wall 22 made of elastic and flexible material delimiting achamber 23, 21 b indicates a front end section connected to intermediatesection 21 a through a front flange 22 a and 21 c indicates a rear endsection connected to intermediate section 21 a through a rear flange 22b.

Front end section 21 b comprises a head 25 conected to front flange 22 aand integral to a stem 24 axially extending through intermediate section21 a and rear end section 21 c and connected to a tubular connector 29.A first clamp 27 is mounted at the end of stem 24 opposite to that wherehead 25 is fixed. Each clamp is formed by a jaw 27 a axially slidable onstem 24 and by a jaw 27 b fixedly connected thereto. Jaw 27 a and 27 bare each formed by a pair of jaw portions diametrically arranged on stem24. The two portions of jaw 27 a are mutually connected by means of abracket 28 passing through a slot 30 diametrically formed in stem 24. Anactuating wire 26 crosses bracket 28 in two points and is fixed to thebracket at one of them while being slidable at the other one. Wire 26slidably extends through the overall length of stem 24 forming a loopalong it and its free ends are conveyed externally through connector 29.Clearly, by pulling one of the two ends from the outside, the openingand closure of clamp 27 can be controlled, as also shown in FIGS. 7 aand 7 b.

As shown in FIGS. 6 a, b, c, rear end section 21 c of the devicecomprises a first sleeve 33 coaxially mounted on stem 24 and slidablethereon. Sleeve 33 has a flanged end one side of which is fixed to rearflange 22 b of intermediate section 21 a, the other one being fixed to abellow 31 coaxial thereto. A pair of arm 33 a, 33 b extend from sleeve33 in a diametrically opposed and parallel relationship with respect tostem 24. Arms 33 a, 33 b are arranged on a plane rotated of an angle of90° with respect to the two jaw portions of first clamp 27 and supportjaws 32 a and 32 b of second clamp 32. Likewise first clamp 27, secondclamp 32 is formed by two diametrically opposed clamp portions andtherefore clamps 27 and 32 are in a substantially crosswise arrangementwith respect to the longitudinal axis of the device, as shown in FIG. 4.

In particular, the pair of portions of jaw 32 a are fixed to the freeends of arms 33 a and 33 b, while the pair of portions of mobile jaw 32b are formed at the end of two further arms 34 a and 34 b extending atthe outside of arms 33 a and 33 b and parallel thereto from a secondsleeve 34 integral to bellow 31 and axially slidable on sleeve 33. Thesliding of arms 34 a, b with respect to arms 33 a, b is limited at oneside by the abutment with fixed jaw 32 a and at the other side by themutual abutment between shoulders 35 and 36 formed on the respectivesliding surfaces.

Tubular connector 29 houses a plurality of pneumatic tubes communicatingto a series of conduits formed in stem 24. In particular, with referenceto FIG. 3, conduits 37 and 38 are provided for creating a depression orfeeding compressed air between jaws 27 a, b of first clamp 27 and jaws32 a, b of second clamp 32, to help engagement and, respectively,release of the surrounding wall portion P of the body cavity, andconduits 45 and 46 to suck or feed air from/to bellows 31 and 22,thereby causing them to extend and respectively to retract. A conduitfor feeding air to head 25 is also provided to blow air against thecavity wall during the forward motion. These conduits are all shown inFIG. 3 for sake of simplicity. Conduits 38 and 45 are helically arrangedinside chamber 23.

The operating cycle of the endoscopic device according to the secondembodiment of the invention is shown in FIGS. 8 a-8 g. First, vacuum iscreated in correspondence of the jaws of second camp 32 to cause asurrounding wall portion P of the body cavity to collapse therebetween(FIG. 8 a), then compressed air is entered in bellows 31 which in thisway is elongated causing the closure of second clamp 32 and the graspingof wall portion P (FIG. 8 b). Compressed air is entered in chamber 23 ofbellows 22 which expands pushing front head 25 forward. In view of theconnection through stem 24 front head 25 pull first clamp 27 forward(FIG. 8 c) After having created a depression between the jaws of firstclamp 27 to make the surrounding wall portion P to collapsetherebetween, first clamp 27 is closed by traction of actuating wire 26to grasp wall portion P (FIG. 8 d). At this point second clamp 32 can beopened by sucking air from bellow 31, to release the wall portion P heldthereby (FIG. 8 e). Once second clamp 32 is opened, it is made toadvance with respect to first clamp 27 by sucking air from bellow 22,which retracts (FIG. 8 f). In these conditions, after second clamp 32 isheld again to the body cavity wall, first clamp 27 is opened and thecycle repeated for a further advancement step.

Opposed grip surfaces of jaws of first and second clamp 27 and 32 areformed with an annular groove and a corresponding step for engagingtherewith to improve the grip of the wall portion of the body cavity.

It will be appreciated that in the second embodiment of the inventionclamps 27 and 32 alternately overtake each other during each advancementstep of the device and the clamp that in turn is in the distal positionis the gripping one, while the other one is free and is pulled forward.This prevents the body cavity wall, due to its easily yielding nature,from retracting into folds together with the device in the retractionstep and extending in the next extension step without achieving any realforward motion of the device.

From the foregoing it is clear that the endoscopic device according tothe invention can migrate through a body cavity of tubular shape apartfrom the consistency of the walls and the friction that can be affordedby them, because it is able to grasp at the cavity wall before exertingits propulsive push. The increased patient's comfort and the reductionof manual handling made possible with the device of the invention couldpromote the possibility of mass screening the population forgasto-itnestinal aliments, in particular to carry out colonoscopy andrectosigmoidoscopy, this being a particularly important inspection, inso far as about 70% of the colon cancers are localized in the firsttract or the colon. In addition to inspection and diagnosis, futureintegration of miniaturized endoscopic tools onboard the locomotivedevice would allow therapeutic procedures to be performed as well.

Several variations may be brought to the above described endoscopicdevice. Front and rear end sections can be removably connected to theintermediate section so as to be easily replaced in case of damage, forexample due to clogging by pollutants, or for maintenance. The wall ofthe intermediate section can be constituted by an elastically extensiblesmooth tube instead of a bellows. The device could be made withdisposable plastic materials, provided that they are suitable forinsertion in a body cavity.

Even if in the present embodiments of the invention pneumaticallyactuated bellows means have been provided for controlling the extensionand the retraction of the intermediate section and the opening andclosing of the clamping means, it is clear that, as an alternative, anyequivalent linear actuating means such as elastic means or minimotors,can be used. Likewise, compressed air distribution can be carried out ina different way from what has been illustrated, for example by usingmicrovalves within the device, possibly controlled with shape memoryalloy actuators.

Further variations and/or modifications can be brought to the endoscopicdevice according to the present invention, without departing from thescope of the invention as set forth in the attached claims.

1. An endoscopic device for locomotion in a body cavity according to aprefixed advancing direction (A) comprising at least a variable lengthintermediate section (1 a, 21 a) extending between a front end section(1 b, 21 b) and a rear end section (1 c, 21 c) with respect to saiddirection and characterized in that it further comprises first andsecond clamping means (7,12,27,32) integral to said front end sectionand, respectively, said rear section, adapted for alternately graspingrespective surrounding portions of wall (P) of said body cavity, andsucking means (13,14,37,38) associated to said first and second clampingmeans for creating a depression sufficient to cause said body cavitywall portions to collapse within said first and second clamping meanswhile they are in an open condition, means for actuating alternateextensions and retractions of said intermediate section and actuatingmeans (6,11,26,31) of said first and second clamping means being furtherprovided for synchronous operation to generate a forward motion in saidprefixed direction of said rear end section due to a retraction of saidintermediate section, the wall portion (P) surrounding said firstclamping means adapted to be firmly held therebetween, and to generate aforward motion of said front end section in the same direction due to anextension of said intermediate section, the wall portion (P) surroundingsaid second clamping means adapted to be firmly held therebetween. 2.The endoscopic device according to claim 1, wherein said first (7) andsecond (12) clamping means are arranged at opposite sides of saidvariable length intermediate section (1 a).
 3. The endoscopic deviceaccording to claim 1, wherein said first (27) and second (32) clampingmeans are arranged at the same side of said variable length intermediatesection (21).
 4. The endoscopic device according to claim 3, whereinsaid first (27) and second (32) clamping means are arranged incorrespondence of rear end section (21 c) thereof.
 5. The endoscopicdevice according to any one of claims 3 and 4, wherein said first (27)and second (32) clamping means are arranged on two perpendicular planesand each comprises a pair of jaws being formed each by a pair ofdiametrical jaw portions.
 6. The endoscopic device according to claims 1or 2, wherein said front/rear end section (1 b/1 c) comprises afront/rear end head (5/8) and a respective stem (4,10) integral to it,to which a jaw (7 b, 12 b) of said first/second clamping means (7,12) isfixed, the other jaw (7 a, 12 a) being slidably mounted on saidrespective stem (4,10).
 7. The endoscopic device according to claim 6,wherein said actuating means of said first clamping means (7) comprise apneumatically extendable and retractable bellows (6) integral to saidslidable jaw (7 a) and said intermediate section (1 a).
 8. Theendoscopic device according to claim 6, wherein said actuating means ofsaid second clamping means (12) comprise a pneumatically extendable andretractable bellows (11) integral to said slidable jaw (12 a) and saidrear head (8), said fixed jaw (12 b) being integral to said intermediatesection (1 a).
 9. The endoscopic device according to claims 1 or 3,wherein said front end section (21 b) comprises a front head (25) and astem (24) integral to said head axially extending through said variablelength intermediate section (21 a) and said rear end section (21 c), atthe free end of said stem a jaw (27 b) of said first clamping means (27)being fixed, the other jaw (27 a) being slidably mounted on said stem(24).
 10. The endoscopic device according to claim 9, wherein saidactuating means of said first clamping means (27) comprise an actuatingwire (26) operable from the outside fixed to said slidable jaw (27 a).11. The endoscopic device according to claim 10, wherein said actuatingwire (26) is fixed to a bracket (28) axially slidable with respect tosaid stem (24) and integral to said slidable jaw (37 a).
 12. Theendoscopic device according to claims 1 or 3, wherein said rear endsection (21 c) comprises a first sleeve (33) integral to said variablelength intermediate section (21 c), a jaw (32 a) of said second clampingmeans (32) being fixed to the free end thereof, the other jaw (32 b)being formed at the end of a second sleeve (34) slidable on said firstsleeve (33).
 13. The endoscopic device according to claim 12, whereinsaid actuating means of said second clamping means (32) comprise abellows (31) for connecting said first and second sleeve (33, 34). 14.The endoscopic device according to claim 12, wherein said first andsecond sleeve (33,34) each comprises a tubular portion coaxial to saidstem (24), respective pair of coplanar and diametrically opposed arms(33 a,b; 34 a, b) extending from said tubular portion for supportingsaid fixed jaw (32 a) and, respectively, said slidable jaw (32 b). 15.The endoscopic device according to claims 1 or 3, wherein said suckingmeans comprise pneumatic conduits (13,14,37,38) formed within said stem(8,10,24) connected to a outside vacuum and compressed air source (50)and outflowing between the jaws of said clamping means (7,12,27,32),said outside source being selectively operated to provide compressed airto be blown between said jaws when they open.
 16. The endoscopic deviceaccording to claims 1 or 3, wherein said intermediate section (1 a, 21a) is formed by a flexible and elastic bellows body (2,22) defining achamber (3,23) and said means for actuating alternate extensions andretractions of said intermediate section (1 a, 21 a) comprise apneumatic conduit (40,46) formed in said stem (10,24) and communicatingwith said chamber (3,23) and said outside vacuum and compressed airsource (50) respectively.
 17. The endoscopic device according to claim7, wherein said bellows (6,11,31) communicate through respectivepneumatic conduits (41,42,38) with said outside vacuum and compressedair source (50) for selectively feeding compressed air or creating adepression therein to cause their extension or retraction.
 18. Theendoscopic device according to claims 1 or 3, wherein said front endsection (1 b, 21 b) is provided with means, for blowing compressed airin said body cavity to cause the surrounding wall thereof to spreadapart during the forward motion, connected through a pneumatic conduit(43,47) to said outside source (50).
 19. The endoscopic device accordingto claim 8, wherein said bellows (6,11,31) communicate throughrespective pneumatic conduits (41,42,38) with said outside vacuum andcompressed air source (50) for selectively feeding compressed air orcreating a depression therein to cause their extension or retraction.20. Method for the locomotion of an endoscopic device through a bodycavity, by means of a succession of extensions and retractions of atleast one variable length intermediate section (1 a, 21 a) in a prefixeddirection (A) defining a front end section (1 b, 21 b) and a rear endsection (1 c, 21 c) of said device, first and second clamping means(7,12,27,32) being associated to said front and, respectively, rear endsection, said first and second clamping means being selectively operablefrom the outside synchronously to said extensions and retractions ofsaid intermediate section, said method being characterized in that apneumatic depression is selectively induced by suction in correspondenceto one of said first (7,27) or second (12,32) clamping means in theiropen conditions, said depression being such that the surrounding wallportion (P) of said body cavity is caused to collapse within saidclamping means, said clamping means being then closed to grasp saidsurrounding wall portion (P) and firmly hold one respective end section(1 b, 1 c, 21 b, 21 c) thereto, thereby allowing the free movement ofthe other end section in the prefixed direction due to extensions andretractions of the intermediate section.
 21. The method according toclaim 20, comprising a series of advancing cycles, each having thefollowing steps: inducing said pneumatic depression by suction incorrespondence to said second clamping means (12,32) in their opencondition, thereby causing the surrounding wall portion (P) to collapsetherewith; —closing said second clamping means (12,32) to grasp saidsurrounding wall portion; —extending said variable length intermediatesection (1 a, 21 a) from a retracted condition to an extended condition;—inducing said pneumatic depression by suction in correspondence to saidfirst clamping means (7,27) in their open conditions to cause thesurrounding wall portion (P) to collapse therewith; —closing said firstclamping means (7,27) to grasp said surrounding wall portion therewith;—opening said second clamping means (12,32) to release said surroundingwall portion therefrom; —retracting said variable length intermediatesection (1 a, 21 a) from said extended condition to said retractedcondition.
 22. Method according to claims 20 or 21, wherein, after eachopening step of said clamping means to release said surrounding wallportion, air is radially blown against it to enlarge said body cavity.23. The method according to claims 20 or 21, wherein the extension orretraction of said variable length intermediate section are performed byadduction or, respectively, suction of a fluid to/from a chamber (3,23)defined in said intermediate section, which is made of a substantiallydeformable material.
 24. The method according to claim 23, wherein saidfluid is air.